EP0382662A1 - Device for the detection of weft thread faults in a weaving machine - Google Patents

Abstract

The device is capable, in particular, of detecting faults relating to the feed of weft yarn. For this purpose, it employs in combination:… - means (8) for detecting the weft yarn (1) on its arrival side at the end of insertion;… - "unweaving" means (16) activated automatically after the detection of an anomaly by the preceding means and after the shutdown of the machine;… - processing and control means (9, 10) taking action on two successive occasions during the "unweaving". …<??>This device is used on a machine with a double feed system (3, 4, 5; 12, 13, 14) for weft yarn (1; 11), with automatic switching from one system to the other in the event of fault. …<IMAGE>…

Description

The present invention relates to a device for detecting defects in the weft thread in a weaving machine. The invention relates in particular to a device capable of detecting faults relating to the weft feed, in particular in a weaving machine provided with a double weft feed system, such as when a fault is detected on one of the supply systems, there is automatic switching to the other supply system, and switching to another weft thread kept on standby, which allows manual troubleshooting on the first feeding system without stopping the operation of the weaving machine.

Already known, from published European patent application No. 0 195 469, a weaving machine provided with a double weft feed system, as specified above. In this weaving machine, several detectors are placed in the path of the weft thread, in each of the two feeding systems. These detectors monitor the state of the weft thread and, in the event of detection of a fault, they control the switching to the other standby supply system, via a control unit.

Such a weaving machine requires, in the two weft feed systems, special detectors which are added to the detection means already provided in the usual way for checking the correct insertion of the weft. In addition, the principle of European patent application No. 0 195 469 is hardly suitable for a weaving machine with pneumatic insertion of the weft by means of air jets ejected by nozzles.

The present invention aims to eliminate these drawbacks by providing an improved device which renders the detectors placed in the supply systems useless by simply using the existing detectors of the "weft breaker" type, this device being applicable without difficulty to weaving machines with pneumatic weft insertion, and more particularly suitable for weaving machines of this kind which are equipped with a so-called "unweaving" system, capable of removing defective wefts in whole picks or pick fragments.

To this end, the subject of the invention is essentially a device for detecting defects in the weft thread in a weaving machine, which use in combination:
- means for detecting the presence or absence of the weft thread, on the side of its arrival at the end of insertion;
- "untwisting" means put into action automatically after detection of any anomaly by the aforementioned means and stopping the weaving machine;
- processing and control means intervening in two successive control times during the "unweaving", in connection with the aforementioned detection means, to restart the weaving machine or to stop it completely or to switch it from a system feed to another weft feed system, depending on the states detected in the first time and in the second control time.

Thus, the device which is the subject of the invention succeeds in distinguishing different types of defects relating to the weft, and in controlling on the weaving machine the actions required by these defects by carrying out an analysis on a first "unweaving", and possibly on a second "untwisting" if a fault persists when the machine is restarted after a first untwisting. All the controls involved in the process are linked to a single detector of the "weft breaker" type, conventional in its design but used here in a particular way, during the "unscrewing": in the first control time, the detection means allow to verify the effective passage of a pick or fraction of pick during extraction, in the second control time, the same detection means make it possible to check the absence of wire, in the case where the pick or fraction of pick has been correctly eliminated in the "untwisting" phase. Other particular cases will be specified below, and the logical analysis carried out by the device makes it possible in particular to detect faults, such as breaks in the weft thread, upstream of the launching nozzle (in the case of a machine to weave with pneumatic weft insertion), therefore in one of the feeding systems, and then to control automatic switching to the other feeding system, with weft yarn kept on standby. This particular type of fault can be effectively detected by an automatic sequence comprising successively:
- A first fault detection by the detection means located on the side of the arrival of the weft thread at the end of insertion;
- a shutdown of the machine followed by a first "untwisting" with control in two stages;
- restarting the machine following which the aforementioned detection means note the persistence of the fault;
- a new shutdown of the machine followed by a second "untwisting" with two-step control showing that when the machine was restarted, no thread was inserted across the width of the fabric .

• Figure 1 est une vue en plan, très schématique, d'une machine a tisser équipée du dispositif objet de la présente invention ;
• Figures 2 et 3 sont des diagrammes illustrant le fonctionnement de ce dispositif.

In any case, the invention will be better understood with the aid of the description which follows, with reference to the appended diagrammatic drawing representing, by way of nonlimiting example, an embodiment of this device for the detection of faults of the weft thread in a weaving machine:

• Figure 1 is a plan view, very schematic, of a weaving machine equipped with the device object of the present invention;
• Figures 2 and 3 are diagrams illustrating the operation of this device.

Referring to FIG. 1, the invention is here described in the case of its application to a weaving machine without shuttle, with pneumatic insertion of the weft thread 1 into the fabric in formation 2, from a reserve of fixed weft located on one side of the fabric 2.

More particularly, the weft thread 1 assumed during weaving comes from a supply spool 3, placed on one side of the weaving machine, and it first arrives at a pre-deliverer 4 which measures corresponding lengths of thread to a pick and which releases the wire in successive lengths each corresponding to a pick. The weft thread 1 then passes through a fixed nozzle 5, then through a launching nozzle 6 mobile with the comb (not shown), the fixed nozzles 5 and mobile 6 being supplied with compressed air to give the wire 1 the initial acceleration necessary for its insertion.

In its crossing of the "crowd" formed by the warp threads, the weft thread 1 is in a known way guided inside an insertion channel, and its movement is maintained by relay nozzles not shown, distributed over the width of the fabric 2 and supplied sequentially with compressed air. Once inserted, each pick is separated from the rest of the weft thread 1 by a cutting means 7 placed at the edge of the fabric 2 on the side of the mobile launch nozzle 6, after which the next pick can be inserted in the same way .

Optical control means 8 of the "weft breaker" type, disposed towards the edge of the fabric 2 remote from the launching nozzle 6, also ensure detection of the actual arrival of the weft yarn 1 as far as this edge of the fabric 2. These control means 8 emit signals directed towards processing means 9, which are themselves connected to a central unit 10 for controlling the weaving machine.

To take into account the possibility of a breakage of the weft thread 1 during weaving, this weaving machine is equipped with additional supply means making it possible to maintain a second weft thread 11 on standby. These means include a second supply reel 12, a second pre-delivery meter 13 and a second fixed nozzle 14, similar to those previously described and located on the same side of the weaving machine. Switching means 15 are provided for controlling, if necessary, the passage from the first supply means 3,4,5 to the other supply means 12,13,14, or vice versa, in particular for continuing weaving with the weft thread. 11 remained on standby, when the weft thread 1 previously used is broken, these switching means being themselves under the control of the central unit 10.

It should be noted that, in the example illustrated in FIG. 1, the mobile launch nozzle 6 is common to the two supply systems, each of the fixed nozzles 5 and 14 directing the corresponding weft thread 1 or 11 towards this nozzle common mobile. One can however envisage a variant not shown in which the mobile nozzles are two in number, like the fixed nozzles 5 and 14, each mobile nozzle being in this case assigned to a separate weft thread.

It should also be noted that the description given above corresponds to the members necessary for the insertion of a weft thread of a single color, and that these members can be multiplied in the case of a weaving machine provided for alternately insert weft threads of several colors.

Finally, the weaving machine considered here is provided with means 16 provided for the extraction of waste from a broken or defective weft thread. These are in particular pneumatic means displaceable over the entire width of the fabric 2, as described in the previous patent application No. 88 07257 filed on May 25, 1988 in the name of the Applicant. These means 16 fulfill a so-called "untwisting" function, in association with a blowing sequence of the relay nozzles.

According to the present invention, the combined action of the means of optical control 8, processing means 9 associated with the latter and "unweaving" means 16 makes it possible to detect a breakage of the weft thread during weaving which occurs upstream of the launching nozzle 6, therefore in the system supply 3,4,5 or 12,13,14 in service. In addition, the intervention of the central unit 10 and the switching means 15 allows, in the event of the detection of such a breakage of the weft thread 1, automatic passage over the weft thread 11 on standby, delivered by the other feeding system, for the immediate continuation of weaving.

These remarkable results are obtained by means of a particular sequence, which will now be described with reference also to the diagrams in FIGS. 2 and 3.

FIG. 2 illustrates the various situations which may be encountered when the optical control means 8 detect an anomaly on the side of the arrival of the weft thread and then control the automatic stopping of the weaving machine. The five successive lines correspond to situations identified A to E in the left column, and shown diagrammatically in the second column where the position of the thread relative to the selvedges of the fabric is represented symbolically.

The third column of the diagram in FIG. 2 indicates the state of control by the optical means 8, during a first "unweaving", carried out after the machine has stopped. These control means intervene in two successive stages; the first control time T1 is located at the start of the "untwisting" action and must make it possible to note the passage of at least one piece of yarn waste being extracted, while the second control time T2 is located at the end of the "untwisting" action, when the yarn waste (s) should in principle be disposed of. The detection of the presence of a wire is symbolized by "1", and the observation of the absence of a wire is symbolized by "O", this for both of the control times T1 and T2 .

• - Situation A : La trame ayant été normalement coupée bien qu'elle soit courte, le "détissage" s'effectue lui-même correctement c'est-à-dire qu'un fragment de fil est éliminé. La machine à tisser est alors remise automatiquement en marche.
• - Situation B : La trame est trop longue et n'est pas éliminée lors du deuxième temps de contrôle T2.
• - Situation C : La trame est au contraire trop courte (et non coupée), son passage n'est pas détecté lors du premier temps de contrôle T1.
• - Situation D : Un mauvais décroisement a provoqué l'accrochage de la trame aux fils de chaîne, de sorte que son évacuation est empêchée.
• - Situation E : La trame est totalement absente dans la largeur du tissu et l'action de "détissage" est là aussi sans effet.

Finally, the right column of the diagram indicates the type of action ordered according to the control state during the first "tightening" after stopping:

• - Situation A: The weft having been normally cut although it is short, the "unweaving" is itself carried out correctly, that is to say that a fragment of thread is eliminated. The weaving machine is then automatically restarted.
• - Situation B: The frame is too long and is not eliminated during of the second T2 control time.
• - Situation C: On the contrary, the frame is too short (and not cut), its passage is not detected during the first T1 control time.
• - Situation D: A poor uncrossing caused the weft to hang on the warp threads, so that its evacuation is prevented.
• - Situation E: The weft is completely absent in the width of the fabric and the "unscrewing" action is also without effect there.

In situations B to E, which are distinguished from situation A by the corresponding control states, the weaving machine is stopped, and a light signal alerts the operator to intervene on site.

• - Situation F : Une nouvelle duite est effectivement insérée après le premier "détissage", mais elle est cassée et trop courte. Cette duite est évacuée correctement lors du deuxième "détissage".
• - Situation G : Une nouvelle duite est là aussi effectivement insérée après le premier "détissage" mais elle est trop longue, ce qui est constaté dans le deuxième temps de contrôle T2.
• - Situation H : Aucun fil n'est inséré dans la largeur du tissu 2, ce qui signifie que le fil de trame était déjà cassé auparavant, et ceci en amont de la buse de lancement 6.

Situation A causes the machine to restart, and in principle the insertion of a new pick. If after this restarting, the optical control means again cause the machine to stop, a new "untwisting" is carried out. The situations that can then be encountered (excluding certain very improbable cases) are illustrated by the diagram in FIG. 3, which uses the same symbolism as in FIG. 2. As before, a check by the optical means 8 is carried out in two successive stages T1 and T2 during this second "untwisting" action. The three types of situations encountered are:

• - Situation F: A new pick is actually inserted after the first "untwisting", but it is broken and too short. This pick is evacuated correctly during the second "unweaving".
• - Situation G: A new pick is also effectively inserted there after the first "untwisting" but it is too long, which is noted in the second T2 control time.
• - Situation H: No thread is inserted in the width of the fabric 2, which means that the weft thread was already broken before, and this upstream of the launching nozzle 6.

In situations F and G, the weaving machine is automatically stopped for manual intervention.

In situation H, perfectly characterized by the corresponding control states "O" and "O" in successive times T1 and T2, the central control unit 10 automatically causes, by means of the switching means 15, the passage to the weft thread 11 on hold, and weaving continues with this thread 11. During this time, the operator can intervene on the weft yarn 1 breaks at the level of the corresponding feeding system, without the operation of the machine being interrupted.

Of course, in the event of a new fault affecting the weft yarn 11 at the level of its feed system, this fault is detected and it is automatically returned to the weft yarn 1, put on hold after repair, by the same process.

The processing means 9, connected to the optical control means 8, detect the control states in the two successive times T1 and T2, translate these states in the form of logic signals "O and" 1 ", and carry out the logical analysis of the combinations of signals obtained at each "untwisting".

The entire automatic sequence of control and permutation of the weft threads can be carried out in a very short time, for example around 20 seconds.

It goes without saying that the invention is not limited to the sole embodiment of this device for detecting weft yarn faults in a weaving machine which has been described above, by way of example. ; on the contrary, it embraces all of the variant embodiments and applications respecting the same principle. Thus, the invention could also be adapted to a weaving machine with a weft feed system not double but simple, which would be provided with means for automatic repair of weft breaks in the feed system.

Claims (3)

1. Device for detecting weft yarn faults in a weaving machine, and in particular device for detecting faults relating to the weft yarn supply, characterized in that it uses in combination:
- Detection means (8) for the presence or absence of the weft thread (1), on the side of its arrival at the end of insertion;
- "unweaving" means (16) activated automatically after detection of any anomaly by the aforementioned means (8) and stopping the weaving machine;
- processing and control means (9,10) intervening in two successive control times (T1, T2) during the "unscrewing", in relation to the aforementioned detection means (8), to restart the machine weaving or completely stopping or switching it from one feeding system (3,4,5) to another feeding system (12,13,14) with weft thread (1; 11), depending on the states detected in the first control time (T1) and the second control time (T2). 2. Device for the detection of weft yarn faults in a weaving machine, according to claim 1, characterized in that it is designed so that during the "unweaving", in the first control time (T1) , the detection means (8) make it possible to check the effective passage of a pick or fraction of pick during extraction, and that in the second control time (T2), the same detection means (8) allow check that there is no wire. 3. Device for detecting defects in the weft thread in a weaving machine, according to claim 1 or 2, characterized in that it is designed to detect defects in the weft thread (1; 11) in a system of feeding (3,4,5; 12,13,14) by an automatic sequence successively comprising:
- a first fault detection by the detection means (8) located on the side of the arrival of the weft thread (1; 11) at the end of insertion;
- a shutdown of the machine followed by a first "untwisting" with two-step control (T1, T2);
- restarting the machine following which the aforementioned detection means (8) note the persistence of the fault;
- a new shutdown of the machine followed by a second "untwisting" with control in two stages (T1, T2) allowing to note when the machine was restarted, no thread was inserted across the width of the fabric (2).

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